Querendaro, Mexico is a tiny town in the west of the country. People had gathered in the main square and waited for the festival to kick-off. Tradition says the mayor is supposed to shout "Viva Mexico!" from the balcony of the town hall. The crowd then answers with the same cry.

Instead, gunmen showed up armed with rifles and grenades, according to the Associated Press. They ordered everyone to clear the square — or die. The men for some reason kept their word, and chose not to fire as people scattered for cover.

Nobody knows who they were, but the size of their guns left little doubt that they're connected to the drug business.

As the cartels grow in power, particularly in the border regions, they've been more likely to attempt to sow fear in ordinary civilians. Last year in Ciudad Juarez, considered a kind of ground zero for drug violence, independence fenstivities were canceled for fear of an outbreak of violence.

In 2008, in Morelia, near Querendaro, gunmen tossed grenades into the main square during the celebration, killing eight people and wounding many more.

The random violence has frustrated many people who say their government isn't doing enough to protect them from the violence. President Felipe Calderon declared a war on drugs in 2006, but its biggest result so far has been the deaths of tens of thousands of Mexican citizens with no connection to the drug trade.